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In fact, NASCAR has collected a rather handy glossary of common racing terms, including one for downforce. It basically states that air pressure moving over a race car's various surfaces creates "downforce" or increased weight. And while downforce increases tire grip and cornering speeds, there's a significant tradeoff -- greater downforce also increases drag, which reduces straightaway speeds [source: NASCAR.com].

­In the past, NASCAR teams were able to run wildly different vehicles. As a matter of fact; each participating manufacturer had its own somewhat unique and recognizable appearance. In recent years, however, NASCAR has attempted to even the playing field by standardizing the body shape race teams are allowed to bring to competition. As a result, the bodywork of every NASCAR Sprint Cup race car is identical regardless of the manufacturer -- with the exception of the paint, of course.

NASCAR's Car of Tomorrow is the current design used exclusively in NASCAR Sprint Cup races. The design increases safety for the driver as the cars go faster and faster each year. But as the speeds increase, for safety's sake, the downforce has to increase as well. The additional downforce increases drag which acts to slow the car down.

­Does this seem like a never ending battle of physics? Well, it is. So we'll take a look at these forces, as they relate to a NASCAR race car, on the next page.